Multi-wavelength (MW) light sources with narrow linewidth are attractive for use in both coherent transmission systems and remote modulation systems. For example, a coherent transmission system requires a narrow linewidth light source when high order modulation, such as quadrature amplitude modulation (QAM), is being used to achieve high capacity. Currently available narrow linewidth light sources are costly to manufacture. Accordingly, narrow linewidth light sources increase the cost of coherent transmission systems, since narrow linewidth light sources are used as both optical carriers and local oscillators, and have been a barrier for coherent detection entering into the short reach market. In a remote modulation system, multiple optical carriers are remotely delivered to reflective type polarization insensitive modulators for data modulation. However, this kind of remote modulation system is susceptible to continuous wave (CW) reflection, where an optical carrier is reflected back by one or more fiber connectors and is combined with its returned optical signal and becomes in-band crosstalk. The impact of CW reflection can be suppressed by using a high pass filter at the receiver to remove the low frequency components generated by the beating of CW reflection and signal carrier. The narrow linewidth of a light source is beneficial to the suppression of the CW reflection. Accordingly, it would be beneficial to develop low-cost narrow linewidth multi-wavelength light sources, for use in both coherent optical transmission systems and remote modulation optical interconnect systems, but not limited thereto.